1. Field of the Invention
This invention is directed to apparatus for counting cycles of reciprocal movement of an object which is moveable in discrete movements of varying length in either direction between two fixed endpoints, and more particularly to such apparatus for recording the reversals of the direction of movement of a valve member which is randomly moved varying amounts in either direction between opened and closed positions.
1. Background Information
One of the factors that affect valve life is how often the valve is cycled. The more a valve is cycled the more likely some parts will be worn. For example, valve packing is sensitive to the number of cycles to which the valve is subjected. Knowledge of how many cycles the valve has experienced may be useful to maintenance personnel in predicting when to maintain the valve.
It is known to provide some valves with limit switches which generate an electrical signal indicating when the valve is in the opened and closed positions. For valves which travel from opened to closed and vice versa without stopping inbetween, such as isolation valves, it is possible to monitor operational cycles of the valve using these stem mounted limit switches to provide electronic pulses for a remote counter. It is also possible to install on such full travel valves mechanical counters to monitor the valve cycles. These possibilities are lost when one wants to know the operating cycles on valves such as control valves where the stroke is generally varying depending upon system flow requirements. In such valves, the valve member may move a fraction of the whole travel, or indeed the whole stroke, between the opened and closed positions. In addition, the valve member may move in one direction, stop and then move again in the same direction. Existing mechanical counters and limit switches actuated at the opened and closed position of a valve are ineffective for monitoring cycles of such random valve member movement since they are capable of measuring only full valve travel.
Accordingly, it is the primary object of this invention to provide apparatus for measuring random cycles of an object which moves in discrete movements of varying lengths in either direction between fixed endpoints.
It is another object of the invention to provide such apparatus which is particularly adapted to measuring random cycles of valve movement in valves where the valve member moves varying amounts in either direction between the opened and closed positions.
It is still another object of the invention to provide means for translating the movements of the object of varying length in either of two reciprocal directions into movements of constant, although adjustable length, suitable for operating cycle counting devices.